fix #30138, reland with windows fix

pkg/dev_compiler/lib/src/compiler/compiler.dart

 // Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 import 'dart:collection' show HashSet, Queue;
 import 'dart:convert' show JSON;
 import 'dart:io' show File;
 
 import 'package:analyzer/analyzer.dart'
     show AnalysisError, CompilationUnit, ErrorSeverity;
@@ skipping 581 matching lines @@
   var uri = Uri.parse(source);
   var scheme = uri.scheme;
   switch (scheme) {
     case "dart":
     case "package":
     case "file":
       // A valid URI.
       return uri;
     default:
       // Assume a file path.
+      // TODO(jmesserly): shouldn't this be `path.toUri(path.absolute)`?
       return new Uri.file(path.absolute(source));
   }
 }